Washington unanimously legalized scissor stairs, a building code reform that frees up to 56% more living space per floor.
Less wasted space means cheaper homes on smaller lots.
Most US states banned this since the 1970s for no good reason.
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Most large apartment buildings are legally required to have two stairwells, e.g., two bulky cores on large lots. Scissor stairs fit into a single core, enabling more homes and more light on smaller lots.
Single-stair reform only helps smaller buildings that need a single exit.
I like this guy's line drawings to help communicate what the resident is doing when using stairs:
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ObamaWellington
@ObamaWellington
Replying to @realsaadasad
For people in the comments not getting how they work:
These buildings also still include elevators. This has to do with fire-safety compliance. Note in the picture on the right, the two 'X' are elevator cabs.
Scissor stairs directly cut circulation from 17% to 12% of each floor.
That also makes narrow buildings viable, which is why Vancouver towers are smaller overall.
The 56% raw difference captures both effects.
Another good visualization:
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Blimp
@BenLP9
Replying to @AlexRMcColl @realsaadasad and @tobyhardtospell
Here you go - good suggestion. AI kept messing up the top I had to crop it :-p
The article refers to the separately enclosed stairwells. You wouldn't see the other stairwell! They just both wrap around the core like a double helix.
I suppose the reason they're banned is that they aren't really independent of each other? My office building has those and I don't really trust them. If they're on fire, there's no way out.
They are enclosed separately. If one has smoke for a reason or one has an emergency, folks going up, the other is still free and unblocked.
NYC is one of only two US cities that kept scissor stairs legal (the other is Dallas), so that tracks. Most of the US banned them in the early 1970s.
The alternative is two fully separate stairwells with independent footprints.
I have stupid questions. How do you get out with this kind of stair? Do you go around through the floor to the next entrance to the zipper stair?
And how does this compare in terms of floor space usage to other stair options?
The two stairways interleave like a double helix within a single core, each with its own door on each floor. You just open your door and walk down a normal stairwell.
Space savings: ~12% of floor used for circulation vs ~17% with conventional stairs.
The goal isn't saving space. It's better-lit apartments, buildings that fit existing neighborhoods, and lower rents. Scissor stairs are just how you get there while maintaining full fire safety compliance.
Translated from French
The concept is equivalent to two separate conventional stairwells in terms of throughput; but here, in the event of a fire, the two scissor staircases end up filled with smoke simultaneously, whereas two separate stairwells offer a better chance of having one that is smoke-free.
You're imagining a slim, narrow building with stairwells at opposite ends, which simply isn't financially or architecturally viable.
The fire-rated walls and self-closing doors prevent smoke spread.
I spent 10 years living in a scissor stair building. It was fine. (I’m Canadian and they’re legal up here).
It's because there's a single source of failure. The point of having 2 separate staircases is to prevent a fire in one from stopping all movement
Scissor stairs satisfy this by keeping the two stairwells physically separated by fire-resistance-rated walls even though they share a single core, so smoke and fire in one can't reach the other.
"no good reason," except for all the preventable deaths
Scissor stairs exist to provide two smoke-isolated escape routes, which is exactly the kind of safety those residents needed.
More importantly, this was an issue of substandard window mesh that helped spread the fire, not stairway design.
The two stairways are enclosed and separated by fire-resistance-rated walls. Their walls ensure that if one stairway is compromised by smoke or fire, residents and emergency responders can safely use the other.
Wouldn’t it make more sense to legalize single stair construction?
Single-stair buildings are smaller.
Scissor stairs are for bigger buildings that require two exits by code. They just let you fit those two exits more efficiently.
Use Claude Code, Windsurf, Codex, Cursor from your phone.
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